STRUCTURE AND LIGHT 169
member layout defines the ingress of natural light. Finally, attention
turns to artificial light sources that are fully integrated with structure, in
contrast to the usual practice of simply mounting or hanging them from
structural members.Some structural forms are far more suited than others to allow daylight
to penetrate into building interiors. For example, the skeletal quality of
structural moment-resisting frames is more conducive to the passage of
light than opaque structural walls. However, other less common struc-
tural forms also provide opportunities to admit light. These areas tend to
occur where different structural systems within the one building meet, as
in the case of the catenary and masted systems at Hall 26, Hanover, and
the Wilkhahn Factory, Bad Münder (see Figs 3.11 and 4.27). In both of
these buildings light penetrates the roof where the catenaries connect to
the masts. In another example at the Stellingen Ice Rink, Hamburg, the
junctions between points of compression support and the fabric roof
serve as direct light sources. Even though the fabric roof is translucent
enough to transmit a small percentage of the external light, openings in
the fabric beneath the mast-tips and above the flying-struts explicitly
invite daylight into the space (Fig. 8.1 and see Figs 3.7 and 3.8).The most common situation where structure functions as a primary
light source occurs where light passes through an open or skeletal struc-
ture like a truss while being excluded from surrounding areas by opaque
cladding. Architects prefer the width, and occasionally the depth of open
structural members as primary daylight sources. Structure rarely acts as
a longitudinal conduit for daylight and well-known precedents are limited
to Kahn’s hollow columns and some of the tubular lattice-columns at
Toyo Ito’s Sendai Mediatheque.^7Daylight is introduced into the central area of San Francisco International
Airport, through specially shaped trusses. While very narrow strip skylights
are positioned immediately above the top chords of the two-dimensional
trusses located near generously glazed side-walls, the middle trusses
widen in order to become sources of light (Figs 8.2 and 8.3). Although
still maintaining the elevational profile of their neighbours, these trusses
have the same lenticular geometry introduced into their plans. Their entire
upper surfaces are fully glazed but direct sunlight is excluded by tautly
stretched translucent fabric. On a sunny day, the space under these trusses
is more brightly illuminated by daylight than the side areas that gain light
directly through the adjacent walls. Whereas the diagonal members in
the side planar trusses consist of both steel tubes and tension rods, the
central three-dimensional trusses use fine rods only to maximize the
intensity of the diffuse light.▲8.1 Stellingen Ice Skating Rink and
Velodrome, Hamburg, Germany, Silcher,
Werner Partners, 1996. Daylight enters the
junction between the flying-strut and the
fabric membrane.